Young internal migrants' major health issues and health seeking barriers in Shanghai, China: a qualitative study.

BACKGROUND: China is experiencing a sizeable rural-urban flow, which may influence the health of internal migrant youth deeply. Disadvantages in the city are highly likely to contribute to health issues among the young internal migrant population. The current qualitative study is to explore how internal migrant young people view the health issues they face, and the services and opportunities they could seek in their host community. METHODS: Data were collected from 90 internal migrant youth aged between 15 and 19 years old and 20 adult service providers who worked with them in a community of Shanghai, where the population of internal migrants was relatively large. Four types of qualitative research methods were used, including key informant interviews with adults, in-depth interviews with adolescents, a photovoice activity with adolescents and community mapping & focus group discussions with adolescents. Guided by the ecological systems framework and the acculturation theory, thematic analysis was conducted using ATLAS.Ti 7.0 software. RESULTS: While younger migrants had a limited understanding of health, elder migrant youths were more sensitive to societal and political factors related to their health. Mental health and health risk behaviors such as smoking, violence and premarital unsafe sex were thought as major health issues. Internal migrant youths rarely seek health information and services initiatively from formal sources. They believed their health concerns weren't as pressing as the pressure coming from the high cost of living, the experience of being unfairly treated and the lack of opportunities. Participants also cited lack of family and social support, lack of awareness and supportive policies to get access to community and public services as impacting health factors. CONCLUSIONS: The study's findings provide the insight to the social contexts which influence the health experience, health seeking behaviors, and city adaptation of young internal migrants in their host community. This research stresses the importance of understanding social networks and structural barriers faced by migrant youth in vulnerable environments. A multidimensional social support is essential for internal migrant youth facing present and potential health risks.

Gender differences in cigarette smoking and alcohol drinking among adolescents and young adults in Hanoi, Shanghai, and Taipei.

OBJECTIVE: This study aimed to examine gender differences in smoking and alcohol drinking behaviors in three Asian cities of Hanoi, Shanghai, and Taipei, and to assess the magnitude of gender differences across the three cities. METHODS: A total of 17,016 adolescents (age: 15-19 years) and young adults (age: 20-24 years) were selected using multi-stage sampling methods and surveyed in face-to-face interviews. A total of 16,554 unmarried respondents were included in this analysis. RESULTS: Gender differences were significant for smoking only, drinking only, and both behaviors in each city. Male respondents were 30.66 times more likely to report smoking only than female respondents in Hanoi, followed by Shanghai and Taipei. This pattern was similar for drinking only and both smoking and drinking behaviors. CONCLUSIONS: The magnitude of gender differences in smoking only, drinking only, and both behaviors widely varies across the three cities. Further research can examine how these differences may be used to prevent and reduce smoking and drinking in the adolescent and young adult population.

Gender role attitudes, awareness and experiences of non-consensual sex among university students in Shanghai, China.

BACKGROUND: Non-consensual sex (NCS) among young people, an important subject with public health and human rights implications, was less studied in China. This study is to investigate the NCS awareness and victimization of university students in Shanghai, China and whether they were associated with adolescent gender-role attitudes. METHODS: Gender-role attitudes, awareness and victimization of different forms of NCS were examined among 1099 undergraduates (430 males and 669 females) in four universities in Shanghai using computer-assisted self-interview approach. RESULTS: University students held relatively egalitarian attitude to gender roles. Gender difference existed that girls desired to be more equal in social status and resource sharing while more endorsed the submissiveness for women in sexual interaction than boys. They held low vigilance on the risk of various forms of NCS, with the mean score on perception of NCS among boys (5.67) lower than that among girls (6.37). Boys who adhered to traditional gender norms were less likely to aware the nature of NCS (ß = - 0.6107, p = 0.0389). Compared with boys, higher proportion of girls had been the victims of verbal harassment, unwanted touch, fondling, and penetrative sexual intercourse. Multivariable analysis revealed that girls who held more traditional gender-role attitudes were more vulnerable to physical NCS (OR = 1.41, p = 0.0558). CONCLUSIONS: The weakening but still existing traditional gender norms had contributions in explaining the gender difference on the low vigilance of NCS and higher prevalence of victimization among university students in Shanghai, China. Interventions should be taken to challenge the traditional gender norms in individual and structural level, and promote the society to understand the nature of NCS better as well as enhance negotiation skills of adolescents and young people that prevent them from potentially risky situations or relationships.

Exposure to bisphenol A (BPA) in Wistar rats reduces sperm quality with disruption of ERK signal pathway.

Bisphenol A (BPA) is an estrogenic environmental toxin widely used in the production of plastics and ubiquitous human exposure to this chemical has been proposed to be a potential risk to human health. Exposure to BPA can negatively impact sperm quality. However, the mechanism remains largely unknown. The objectives of this study were to assess the role of BPA on sperm quality and explore the possible mechanisms. The Wistar male rats (aged 28 days) were administered BPA by oral gavage for 28 days at dose of 50, 100 and 200 mg/kg/day; meanwhile, the negative control with corn oil (0 mg/kg/day BPA) and positive control with E2 at the dose of 100 µg/kg/day. The sperm density, sperm activity and sperm survival rate were analyzed byCASA system, and the sperm abnormality rate was analyzed by improved Papanicolaou stained. The protein expression levels of Src/p-Src, ERK1/2, p-ERK1/2 and CREB/p-CREB were detected by Western bolt. The results showed that the body weight gain, testes weight, testis coefficient, sperm density, sperm activity, sperm survival rate and protein expression levels of p-ERK1, p-ERK2 and p-CREB decreased, but the sperm abnormality rate increased with increasing BPA concentrations. There were positive correlations between sperm density, sperm activity and sperm survival rate with protein expression levels of p-ERK1, p-ERK2 and p-CREB, and negative correlations between sperm abnormality rate with the protein expression levels of p-ERK1, p-ERK2 and p-CREB. Results from the structural equation model demonstrated that BPA retained a significant negative effect to p-ERK, whereas p-ERK retained a significant positive effect to sperm quality and acted as the mediate variable. This study provides a novel insight regarding the potential role of p-ERK1 and p-ERK2 protein kinase on reproductive toxicity of BPA. The adverse effects of BPA on adult male sperm quality may be through the induction of the disruption of ERK signal pathway. However, additional research is needed to confirm our findings and to further test the suggested potential mechanisms.

Single or double semen samples: the dilemma in epidemiological studies on semen quality.

STUDY QUESTION: Is it necessary to collect more than one semen sample from each individual in epidemiological studies? SUMMARY ANSWER: Single semen samples can be used in model construction as long as the model adjusts for major relevant covariates. WHAT IS KNOWN ALREADY: If a series of semen samples are taken from one individual at different times, significant intra-individual variation may exist. STUDY DESIGN, SIZE, DURATION: A population-based cross-sectional study was conducted from 1 December 2000 to 20 November 2002. A total of 1010 volunteers, aged between 20 and 60 years old, were recruited. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 998 subjects were included for statistical analysis. Of these, 332 men provided single semen samples (group 1) and 666 men provided two samples (group 2). Semen parameters, including semen volume, sperm concentration, total sperm number, progressive motility, vitality, and sperm morphology, were analyzed with standardized methods according to the World Health Organization (WHO) laboratory manual for the examination of human semen and sperm-cervical mucus interaction (3rd edition). MAIN RESULTS AND THE ROLE OF CHANCE: Rapidly progressive motility of semen from group 1 was lower than that of group 2, but other parameters were not significantly different. The differences in mean values between the double samples were small on all semen parameters. The correlations between the two ejaculates were high, but the agreements were poor except for sperm vitality and normal morphology. Model selection and validation analysis supported the premise that the regression model from the first samples was applicable for the second samples. The large sample size with extensive quality control provides robust parameter estimation and promises good applicability for model selection and validation. LIMITATIONS, REASONS FOR CAUTION: The results are valid for healthy men in China, not for subfertile or infertile men. WIDER IMPLICATIONS OF THE FINDINGS: The overall semen quality of a given group of healthy men will not vary significantly in the short term. Single semen samples can be used in model building as long as major relevant covariates are considered. Utilizing multiple semen donations may actually cause the samples to be less representative. STUDY FUNDING/COMPETING INTERESTS: This research was supported by a grant from Shanghai Science and Technical Committee (02DJ14053) and a grant from Ministry of Science and Technology, China (9902). All authors have no competing interests.

Association between environmental exposure to cadmium and human semen quality.

Cadmium (Cd) is a heavy metal with toxicant to reproductive functions. The aim of this study was to explore the effects of environmental exposure to Cd on human semen quality. A total of 587 men from the general population, aged from 20 to 59 years old, and without occupational exposure to Cd were recruited from three provinces in China to participate in the study. The median of serum Cd was 1.9 µg/L (P25-P75:1.1-2.9). In case Cd was less than or equal to 6.3 µg/L (P95) and the semen parameters were logarithmically transformed, the inverse associations between Cd and semen volume (-0.03 ± 0.007), progressive motility (-0.01 ± 0.004), and sperm morphology (-0.04 ± 0.004) were found across the whole group, after adjusting for age group, occupation, season of semen sample collection, abstinence intervals, smoking, alcohol drinking, and body mass index. Our findings indicate that higher Cd may reduce the semen volume, progressive motility, and morphology among men without occupational exposure to Cd.

Patterns of sexual behaviors among unmarried adolescents and youth in three Asian cities.

We examined patterns of sexual behaviors of unmarried adolescents and youth (UAY) in three Asian cities (Shanghai, Taipei, and Hanoi) and identified factors related to the timing of initial sexual experience. From analysis of a sample of 16,554 UAY aged 15-24 years recruited from Shanghai, Taipei, and Hanoi plus data collected from face-to-face interviews complemented by computer-assisted self-interviews for intimate questions, we learned: UAY in Shanghai, Taipei, and Hanoi have different sexual behaviors. Affluent economic status increases the likelihood of early initial sexual experiences. Higher educational attainment may delay initial intercourse. Compared with Shanghai UAY, study participants from Taipei and Hanoi were 3.64 times and 0.33 times as likely to participate intercourse. These data can provide a basis for developing effective government policies and social interventions.

Associations between Bisphenol A Exposure and Reproductive Hormones among Female Workers.

The associations between Bisphenol-A (BPA) exposure and reproductive hormone levels among women are unclear. A cross-sectional study was conducted among female workers from BPA-exposed and unexposed factories in China. Women's blood samples were collected for assay of follicle-stimulating hormone (FSH), luteinizing hormone (LH), 17ß-Estradiol (E2), prolactin (PRL), and progesterone (PROG). Their urine samples were collected for BPA measurement. In the exposed group, time weighted average exposure to BPA for an 8-h shift (TWA8), a measure incorporating historic exposure level, was generated based on personal air sampling. Multiple linear regression analyses were used to examine linear associations between urine BPA concentration and reproductive hormones after controlling for potential confounders. A total of 106 exposed and 250 unexposed female workers were included in this study. A significant positive association between increased urine BPA concentration and higher PRL and PROG levels were observed. Similar associations were observed after the analysis was carried out separately among the exposed and unexposed workers. In addition, a positive association between urine BPA and E2 was observed among exposed workers with borderline significance, while a statistically significant inverse association between urine BPA and FSH was observed among unexposed group. The results suggest that BPA exposure may lead to alterations in female reproductive hormone levels.

The relationship between age at menarche and infertility among Chinese rural women.

OBJECTIVE: To explore the relationship between age at menarche and infertility. STUDY DESIGN: The cross-sectional study investigated 6906 couples from the communities in Sandu Shui Autonomous County of Guizhou Province, China. Face to face interviews were conducted to collect information on age at menarche and time to first pregnancy, as well as demographic characteristics and lifestyle factors. Infertility was defined as being unable to become pregnant after attempting for ≥12 months. Poisson regression was used to assess the relationship between age at menarche and infertility of first attempt. RESULTS: The prevalence rate of infertility for the first pregnancy attempt of the study population was 11.87%. There is an obvious monotonic, almost linear, trend of prevalence rate of infertility with increasing age at menarche (P for trend: <0.001). Compared with wives with age at menarche of 13 years, the prevalence ratios of infertility were 0.71 (95%CI: 0.42, 1.20), 1.33 (95%CI: 1.05, 1.68), 1.47 (95%CI: 1.17, 1.85), 1.57 (95%CI: 1.20, 2.04), 1.41 (95%CI: 1.00, 1.99) and 1.73 (95%CI: 1.18, 2.52) for wives with age at menarche of ≤12, 14, 15, 16, 17 and ≥18 years, respectively, after adjusting for wife's year at birth, age at marriage, ethnic group, education and occupation, and husband's smoking and drinking habits before marriage. CONCLUSIONS: The present community-based study indicated that increasing age at menarche was associated with an increased risk of infertility in the study population.

Exposure to bisphenol-A and reproductive hormones among male adults.

BACKGROUND: Bisphenol A (BPA) is a suspected human endocrine disruptor which is widely used. METHODS: In order to determine whether urine BPA level is associated with serum reproductive hormone levels among male adults, we carried out a cross-sectional study in China. We recruited 592 male workers and collected their urine samples for BPA measurement. We also collected blood samples and examined serum reproductive hormones. We used multiple linear regression and log-binomial model to examine associations between urine BPA level and hormone levels after controlling for age and smoking status. RESULTS: An increased urine BPA level was associated with increased prolactin (p<0.001), estradiol (p<0.001), sex hormone-binding globulin level (p=0.001), and a reduced androstenedione (p<0.001) and free androgen index level (p=0.021). Males, whose urine BPA level was in the 2nd, 3rd and highest quartiles, had respectively 1.58, 1.33 and 3.09-fold increased prevalence of having a high prolactin level (>P75 level). The highest quartile of BPA level was associated with 1.63 and 1.50-fold increased prevalence of having a high estradiol and elevated sex hormone-binding globulin level. Males with higher quartile of BPA level had a lower inhibin B level. CONCLUSION: High BPA exposure is associated with increased prolactin, estradiol and sex hormone-binding globulin level in males, and may contribute to male infertility.

Sexual orientation and smoking history: results from a community-based sample of youth in Shanghai, China.

OBJECTIVE: Cigarette smoking has been found to be more prevalent among adults and youths with a minority sexual orientation (lesbian, gay, bisexual, LGB) than among the general population, while less is known about smoking among LGB youth in low- and middle-income countries. The goal of the study was to examine cigarette smoking in relation to sexual orientation in a community-based sample of youth in Shanghai, China. METHODS: A multi-center cross-sectional survey of 17,016 youth aged 15-24 years was conducted in rural and urban areas of Hanoi, Vietnam; Taipei, Taiwan; and Shanghai, China in 2006. In this article, analysis was restricted to the 6,299 respondents in Shanghai. Assessments included ever smoking, age at first smoking, frequency of smoking, and number of cigarettes smoked daily. Logistic regression was used to estimate the association between sexual orientation and cigarette smoking. RESULTS: Nine percent (594/6,299) of eligible participants considered themselves as LGB youths; 34.2% ever smoked, 14.81% initiated smoking before age 13, 15.9% smoked in the past 30 days, and 14.1% were moderate or heavy smokers. LGB identity predicted moderate or heavy smoking (OR 2.2, 95% CI 1.3, 3.9). Male LGB youth smoked more cigarettes daily (OR 2.2, 95% CI 1.3, 3.9) whilst female LGB youth reported less any prior cigarette use (OR 0.7, 95% CI 0.5, 1.0). CONCLUSIONS: Few meaningful disparities in cigarette smoking were related to sexual orientation, except male LGB youth consumed more cigarettes daily. Prevention and cessation should target this population, especially male LGB youth.

Child Sexual Abuse and Its Relationship With Health Risk Behaviors Among Adolescents and Young Adults in Taipei.

This study explores the association of child sexual abuse (CSA) with subsequent health risk behaviors among a cross-section of 4354 adolescents and young adults surveyed in urban and rural Taipei. Descriptive analysis and logistic regressions were employed. The overall proportion of CSA was 5.15%, with more females (6.14%) than males (4.16%) likely to experience CSA. CSA was differently associated with multiple adverse health outcomes, after adjusting other factors, such as age, residence, economic status, education, employment status, and household instability. Both males and females with CSA experience were more likely to report drinking, gambling, and suicidal ideation compared with those who had no history of CSA. However, the significant association between CSA and smoking, fighting, and suicidal attempt was not observed among females. Effective interventions are needed to reduce CSA and its adverse effects on adolescent well-being.

Sexual orientation and risk factors for suicidal ideation and suicide attempts: a multi-centre cross-sectional study in three Asian cities.

PURPOSE: Despite robust empirical and theoretical evidence for higher rates of suicide among lesbian, gay, and bisexual (LGB) youths, little is known about the relationship between suicide and sexual orientation among Asian youths. This study examined differences in prevalence of suicidal ideation and suicide attempts between LGB and heterosexual youths in the cities of Hanoi, Shanghai, and Taipei, China. METHODS: The data are from a community-based multi-centre cross-sectional study conducted from 2006 to 2007, with a sample of 17 016 youths aged 15-24 years from Hanoi, Shanghai, and Taipei. Chi-square test and logistic regression were used to evaluate correlates of suicidal ideation and suicide attempts. RESULTS: The overall prevalence of suicidal ideation and suicide attempts in the preceding 12 months in LGB youths were both higher than in heterosexual youth (12.8% vs. 8.1% and 4.0% vs. 2.4%, respectively). Stratified by city, the prevalence of suicidal ideation was lowest in Hanoi (2.2%), followed by Shanghai (8.0%) and Taipei (17.0%). Similar trends were observed in the prevalence of suicide attempts, which was lowest in Hanoi (0.3%), followed by Shanghai (1.2%) and Taipei (2.5%). Of note, however, multivariate logistic regression results revealed that LGB youth were at a higher risk for suicidal ideation than heterosexual youth only in Taipei (odds ratio 1.65). CONCLUSIONS: Suicidality is common among Asian youth, with higher prevalence observed in urbanized cities. LGB youths are at greater risk of suicidal ideation than their heterosexual counterparts in Taipei than in the other two examined cities.

Drunkenness and its association with health risk behaviors among adolescents and young adults in three Asian cities: Hanoi, Shanghai, Taipei.

PURPOSE: To assess the prevalence of drunkenness among adolescents in Hanoi, Shanghai, and Taipei and explore the association between heavy drinking and other health risk behaviors. METHODS: The data are drawn from the Three-city Collaborative Study of Adolescent Health, conducted in Hanoi, Shanghai, and Taipei in 2006. A sample of 17,016 adolescents and young adults, aged 15-24 years, was selected by multistage sampling. Descriptive analysis was used to estimate the proportion of drunkenness and other health risk behaviors. Multivariate logistic regression was used to investigate relationships between drunkenness and risky health behaviors. RESULTS: The proportions of the sample getting drunk during the past month were 6.36%, 4.53%, and 8.47% in Hanoi, Shanghai, and Taipei, respectively. More males than females reported drunkenness in all three cities, with the difference highest in Hanoi (11.08% vs. 1.14%) and lowest in Taipei (9.69% vs. 7.18%). Different levels of relationship between drunkenness and health risk behaviors, such as anxiety, suicidal ideation, smoking, gambling, fighting, drinking and driving, and having sexual intercourse, were found across the three cities; an exception was nonuse of contraception. CONCLUSION: Drunkenness was positively associated with many health risk behaviors. It may serve as an indicator of other risky behaviors. Interventions to reduce drinking and drunkenness may contribute considerably to the prevention of other risk behaviors and to adolescent safety and well-being.

Respondent-driven sampling for an adolescent health study in vulnerable urban settings: a multi-country study.

The global adolescent population is larger than ever before and is rapidly urbanizing. Global surveillance systems to monitor youth health typically use household- and school-based recruitment methods. These systems risk not reaching the most marginalized youth made vulnerable by conditions of migration, civil conflict, and other forms of individual and structural vulnerability. We describe the methodology of the Well-Being of Adolescents in Vulnerable Environments survey, which used respondent-driven sampling (RDS) to recruit male and female youth aged 15-19 years and living in economically distressed urban settings in Baltimore, MD; Johannesburg, South Africa; Ibadan, Nigeria; New Delhi, India; and Shanghai, China (migrant youth only) for a cross-sectional study. We describe a shared recruitment and survey administration protocol across the five sites, present recruitment parameters, and illustrate challenges and necessary adaptations for use of RDS with youth in disadvantaged urban settings. We describe the reach of RDS into populations of youth who may be missed by traditional household- and school-based sampling. Across all sites, an estimated 9.6% were unstably housed; among those enrolled in school, absenteeism was pervasive with 29% having missed over 6 days of school in the past month. Overall findings confirm the feasibility, efficiency, and utility of RDS in quickly reaching diverse samples of youth, including those both in and out of school and those unstably housed, and provide direction for optimizing RDS methods with this population. In our rapidly urbanizing global landscape with an unprecedented youth population, RDS may serve as a valuable tool in complementing existing household- and school-based methods for health-related surveillance that can guide policy.

Prevalence and Health Impact of Intimate Partner Violence and Non-partner Sexual Violence Among Female Adolescents Aged 15-19 Years in Vulnerable Urban Environments: A Multi-Country Study.

PURPOSE: Globally, adolescent women are at risk for gender-based violence (GBV) including sexual violence and intimate partner violence (IPV). Those in economically distressed settings are considered uniquely vulnerable. METHODS: Female adolescents aged 15-19 from Baltimore, Maryland, USA; New Delhi, India; Ibadan, Nigeria; Johannesburg, South Africa; and Shanghai, China (n = 1,112) were recruited via respondent-driven sampling to participate in a cross-sectional survey. We describe the prevalence of past-year physical and sexual IPV, and lifetime and past-year non-partner sexual violence. Logistic regression models evaluated associations of GBV with substance use, sexual and reproductive health, mental health, and self-rated health. RESULTS: Among ever-partnered women, past-year IPV prevalence ranged from 10.2% in Shanghai to 36.6% in Johannesburg. Lifetime non-partner sexual violence ranged from 1.2% in Shanghai to 12.6% in Johannesburg. Where sufficient cases allowed additional analyses (Baltimore and Johannesburg), both IPV and non-partner sexual violence were associated with poor health across domains of substance use, sexual and reproductive health, mental health, and self-rated health; associations varied across study sites. CONCLUSIONS: Significant heterogeneity was observed in the prevalence of IPV and non-partner sexual violence among adolescent women in economically distressed urban settings, with upwards of 25% of ever-partnered women experiencing past-year IPV in Baltimore, Ibadan, and Johannesburg, and more than 10% of adolescent women in Baltimore and Johannesburg reporting non-partner sexual violence. Findings affirm the negative health influence of GBV even in disadvantaged urban settings that present a range of competing health threats. A multisectoral response is needed to prevent GBV against young women, mitigate its health impact, and hold perpetrators accountable.

[Situation of domestic violence and health outcomes among married migrant women at reproductive age].

OBJECTIVE: To examine the association between domestic violence and mental/general health status among married migrant women at reproductive age. METHODS: A total of 958 eligible married migrant women of reproductive age who were selected through community-based multiple-stage sampling method in one urban district in Shanghai and interviewed in April and May 2010. Chi-square test, Fisher's exact test and unconditional logistic regression model were used for data analysis. RESULTS: The overall prevalence of domestic violence in husbands was 40.0%. Among 5 adverse outcomes related to general health and 6 adverse outcomes related to mental health, exposing to physical or sexual violence in the life time or in the previous year were associated with 2 adverse outcomes related to general health (including often in pain/discomfort and sleeping problems) and 4 adverse outcomes related to mental health (including often feeling nervous/tense/worry, easily getting frightened, crying more than usual, often feeling worthless on herself or being indifferent to the surroundings). Experience of control behavior was associated with 1 adverse outcome that related to general health (often in pain or discomfort) and 3 adverse outcomes related to mental health including easily get frightened, feeling worthless on herself or indifferent to the surroundings, Experience of emotional violence in the previous year was associated with pain or discomfort feelings. Compared with those who had never experienced any violence from husband after adjusting for potential influencing factors in logistic regression models, respondents who had ever experienced physical or sexual violence, control behavior or emotional violence, the numbers were respectively, presented 2.25-3.70 times, 1.94-4.75 times and 2.12 times, more likely to report the above-mentioned adverse health outcomes. CONCLUSION: Domestic violence was associated with general and mental health among married migrant women at reproductive age, especially physical or sexual violence and control behaviors.

Induced abortion and breast cancer: results from a population-based case control study in China.

AIM: To determine whether induced abortion (IA) increases breast cancer (BC) risk. MATERIALS AND METHODS: A population-based case-control study was performed from Dec, 2000 to November, 2004 in Shanghai, China, where IA could be verified through the family planning network and client medical records. Structured questionnaires were completed by 1,517 cases with primary invasive epithelial breast cancer and 1,573 controls frequency- matched to cases for age group. The information was supplemented and verified by the family planning records. Statistical analysis was conducted with SAS 9.0. RESULTS: After adjusting for potential confounders, induced abortions were not found to be associated with breast cancer with OR=0.94 (95%CI= 0.79-1.11). Compared to parous women without induced abortion, parous women with 3 or more times induced abortion (OR=0.66, 95%CI=0.46 to 0.95) and women with 3 or more times induced abortion after the first live birth (OR=0.66, 95%CI =0.45 to 0.97) showed a lower risk of breast cancer, after adjustment for age, level of education, annual income per capita, age at menarche, menopause, parity times, spontaneous abortion, age at first live birth, breast-feeding, oral contraceptives, hormones drug, breast disease, BMI, drinking alcohol, drinking tea, taking vitamin/calcium tablet, physical activity, vocation, history of breast cancer, eating the bean. CONCLUSIONS: The results suggest that a history of induced abortions may not increase the risk of breast cancer.

An Empirical Analysis of the Impact of Recruitment Patterns on RDS Estimates among a Socially Ordered Population of Female Sex Workers in China.

Respondent-driven sampling (RDS) is a method for recruiting "hidden" populations through a network-based, chain and peer referral process. RDS recruits hidden populations more effectively than other sampling methods and promises to generate unbiased estimates of their characteristics. RDS's faithful representation of hidden populations relies on the validity of core assumptions regarding the unobserved referral process. With empirical recruitment data from an RDS study of female sex workers (FSWs) in Shanghai, we assess the RDS assumption that participants recruit nonpreferentially from among their network alters. We also present a bootstrap method for constructing the confidence intervals around RDS estimates. This approach uniquely incorporates real-world features of the population under study (e.g., the sample's observed branching structure). We then extend this approach to approximate the distribution of RDS estimates under various peer recruitment scenarios consistent with the data as a means to quantify the impact of recruitment bias and of rejection bias on the RDS estimates. We find that the hierarchical social organization of FSWs leads to recruitment biases by constraining RDS recruitment across social classes and introducing bias in the RDS estimates.

The effect of high birth weight on overweight and obesity in childhood and adolescence. A cohort study in China.

OBJECTIVES: To determine the association of high birth weight (HBW) with the risk of obesity in childhood and adolescence. We also aimed to explore the interactions of HBW with physical activity and dietary habits. METHODS: In a birth cohort born in 1993, 1994, and 1995 in Wuxi, China, subjects with a birth weight (BW) of >/=4000 g were selected as the exposed group. For each exposed subject, one non-exposed subject with a BW of 2500-3999 g, matched by year of birth, gender, and type of institute at birth was chosen. Two follow-ups were performed from October 2005 to February 2007 and July 2010 to December 2011. RESULTS: A total of 1108 exposed and 1128 non-exposed subjects were included. Overweight/obesity rates were significantly higher in the exposed group (16.2% in childhood and 14.2% in adolescence) than those in the non-exposed group (12.1% in childhood and 8.2% in adolescence). There was no significant interaction between BW and the growth period (F=2.10, p=0.147). The relative excess risk due to interaction (RERI) of HBW with physical activity was -0.20 (95% CI=-2.85-2.45), and the RERI of HBW with dietary habits was 1.19 (95% CI=0.14-2.23). CONCLUSION: Infants with HBW are at increased risk of childhood and adolescent overweight/obesity, and this relationship is not influenced by the growth period. There is an additive interaction between HBW and dietary habits.